Methods for reducing aldehyde emissions in polyurethane foams

ABSTRACT

Polyurethane foams are made by curing a reaction mixture that contains an aromatic polyisocyanate, at least one isocyanate-reactive material having an average functionality of at least 2 and an equivalent weight of at least 200 per isocyanate-reactive group, at least one blowing agent, at least one surfactant and at least one catalyst, a polyethyleneamine mixture having a number average molecular weight of 175 to 450 and an alkali metal, phosphonium or ammonium sulfite. Foams so produced emit low levels of formaldehyde, acetaldehyde, acrolein and propionaldehyde.

This invention relates to polyurethanes that exhibit low levels ofaldehyde emissions, and to methods for producing such polyurethanes.

Polyurethane foams are used in many office, household and vehicularapplications. They are used, for example, in appliance applications andas cushioning for bedding and furniture. In automobiles and trucks,polyurethanes are used as seat cushioning, in headrests, in dashboardsand instrument panels, in armrests, in headliners, and otherapplications.

These polyurethanes often emit varying levels of aldehydes such asformaldehyde, acetaldehyde, acrolein (propenyl aldehyde) andpropionaldehyde. Because of the cellular structure of these foams,aldehydes contained in the foam easily escape into the atmosphere. Thiscan present an odor concern and an exposure concern, especially whenpeople or animals are exposed to the material within an enclosed space.Vehicle manufacturers are imposing stricter limits on the emissions frommaterials that are used in the passenger cabins of cars, trucks, trainsand aircraft.

Scavengers are sometimes used to reduce aldehyde emissions from varioustypes of materials. In the polyurethane field, there is, for example, WO2006/111492, which describes adding antioxidants and hindered aminelight stabilizers (HALS) to polyols to reduce aldehydes. WO 2009/114329describes treating polyols with certain types of aminoalcohols andtreating polyisocyanates with certain nitroalkanes, in order to reducealdehydes in the polyols and polyisocyanates, respectively, and inpolyurethanes made from those materials. JP 2005-154599 describes theaddition of an alkali metal borohydride to a polyurethane formulationfor that purpose. U.S. Pat. No. 5,506,329 describes the use of certainaldimine oxazolidine compounds for scavenging formaldehyde frompolyisocyanate-containing preparations, and describes nitroalkanes andaminoalcohols as formaldehyde scavengers in textile and plywoodapplications.

These approaches provide limited benefit, in part because aldehydespresent in polyurethane foam are not always carried in from the rawmaterials used to make the foam. Formaldehyde and acetaldehyde inparticular can form during the curing step or when the foam is latersubjected to UV light, elevated temperatures or other conditions. Inaddition, measures that are effective against formaldehyde emissions arenot always effective against acetaldehyde, acrolein or propionaldehydeemissions, and vice versa. In some cases, measures that are effective inreducing acetaldehyde emissions can actually cause an increase informaldehyde emissions. Applicants have further found that the presenceof HALS often leads to an increase in formaldehyde emissions,acetaldehyde emissions or both.

PCT/CN2017/073764 describes the use of aminoalcohols together withcertain antioxidants to reduce aldehyde emissions from polyurethanefoam. This combination provides some improvement, but a greaterreduction of aldehyde emissions is wanted.

US2017/0088497 describes polyol compositions that containpolyethyleneimines and and alkali metal bisulfite. A 2500 molecularweight polyethyleneimine material is described in the examples. Thecombination of this 2500 molecular weight polyethyleneimine and sodiumbisulfite was effective in reducing formaldehyde and acetaldehydeemissions. However, still better performance is wanted.

Therefore, a method for effectively and economically reducingformaldehyde, acetaldehyde, acrolein and propionaldehyde emissions iswanted. Preferably, this method does not result in a significant changein the properties or performance of the polyurethane.

This invention is a process for producing a polyurethane foam comprisingforming a reaction mixture that contains an aromatic polyisocyanate, atleast one isocyanate-reactive material having an average functionalityof at least 2 and an equivalent weight of at least 200 perisocyanate-reactive group, at least one blowing agent, at least onesurfactant and at least one catalyst, and curing the reaction mixture inthe presence of (i) a polyethyleneamine mixture having a number averagemolecular weight of 175 to 450 and (ii) an alkali metal, ammonium orphosphonium sulfite, to form the polyurethane foam.

The invention is also a process for reducing aldehyde emissions from apolyurethane foam, comprising: a) combining (i) a polyethyleneaminemixture having a number average molecular weight of 175 to 450 and (ii)an alkali metal, ammonium or phosphonium sulfite with at least oneisocyanate-reactive material having an average functionality of at least2 and an equivalent weight of at least 200 per isocyanate-reactive groupto form a mixture and then b) combining the mixture from step a) with atleast one organic polyisocyanate and curing the resulting reactionmixture in the presence of at least one blowing agent, at least onesurfactant and at least one catalyst to form a polyurethane foam.

The invention is also a polyurethane foam made in either of theforegoing processes.

The combination of the a polyethyleneamine mixture having a numberaverage molecular weight of 175 to 450 and alkali metal, ammonium orphosphonium sulfite has been found to reduce the levels of each offormaldehyde, acetaldehyde, acrolein and propionaldehyde emitted by thepolyurethane foam.

To produce foam in accordance with the invention, at least onepolyisocyanate is reacted with at least one isocyanate-reactive compoundthat has a functionality of at least 2 and an equivalent weight of atleast 200 per isocyanate-reactive group. Other ingredients may bepresent as discussed hereinbelow. The reaction is performed in thepresence of the a polyethyleneamine mixture having a number averagemolecular weight of 175 to 450 and/or hydroxylamine and the alkalimetal, ammonium or phosphonium sulfite.

The a polyethyleneamine mixture having a number average molecular weightof 175 to 450 and alkali metal, ammonium or phosphonium sulfite can beprovided as a mixture with any one or more of the various ingredients ofthe formulation used to produce the foam. Alternatively, these may beadded into the reaction as a separate component or stream without beingpreviously combined with any of the other ingredients.

Preferably, however, the a polyethyleneamine mixture having a numberaverage molecular weight of 175 to 450 and alkali metal, ammonium orphosphonium sulfite are blended with the isocyanate reactive compound(s)that have at least two isocyanate-reactive groups per molecule and anequivalent weight of at least 200 per isocyanate-reactive group, priorto forming the polyurethane foam. The resulting blend is maintained atapproximately room temperature or a higher temperature (but below theboiling temperature of the polyethyleneamine mixture having a numberaverage molecular weight of 175 to 450 and below the temperature atwhich the polyol degrades) for a period of at least 30 minutes prior tomaking the foam. Such a blend may be maintained under such conditionsfor any arbitrarily longer time, such as up to a month, up to a week, orup to a day.

A suitable amount of a polyethyleneamine mixture having a number averagemolecular weight of 175 to 450 is from 0.01 to 1 pph (i.e., 0.10 to 1parts by weight per 100 parts by weight of isocyanate reactivecompound(s) that have at least two isocyanate-reactive groups permolecule and an equivalent weight of at least 200 perisocyanate-reactive group). The amount of polyethyleneamine mixturehaving a number average molecular weight of 175 to 450 may be at least0.02, at least 0.03 pph or at least 0.04 pph and may be up to 0.5 pph,up to 0.25 pph, up to 0.15 pph or up to 0.1 pph.

The polyethyleneamine mixture is a mixture of linear, branched and/orcyclic polyethyleneamines. Polyethyleneamines are chemical compoundscharacterized in having multiple —CH₂—CH₂—NH— groups.

The number average molecular weight of the polyethyleneamine mixture maybe, for example, at least 200 or at least 225. It may be up to 400, upto 350 or up to 325. Although the number average weight should fallwithin the aforementioned ranges, the polyethyleneamine mixturetypically will contain a range of polyehthyleneamine molecules havingvarious molecular weights, some proportion of which may have molecularweights lower than 175 or higher than 450. This is acceptable providedthe number average molecular weight falls within the ranges describedabove. The polyethyleneamine mixture preferably contains no more than 10weight percent, especially no more than 5 weight percent or no more than2 weight percent, of polyethyleneamines having a molecular weight of 125or lower. Similarly, the polyethyleneamine mixture preferably containsno more than 10 weight percent, especially no more than 5 weight percentor no more than 2 weight percent, of polyethyleneamines having amolecular weights of 600 or higher.

The polyethyleneamines contained within the polyethyleneamine mixturemay include, for example, compounds having either of the followingstructures I and II:

wherein x and y each are positive numbers, z is zero or a positivenumber and each R is independently hydrogen, ethyleneamine or linear,branched and/or cyclic polyethyleneamine. x, y and z are selected suchthat the number average molecular weight of the polyethylenamine is asdescribed before. For particular compounds within the polyethyleneaminemixture, x is preferably 3 to 17, especially 6 to 12. When each R ishydrogen, y+z is preferably 3 to 17, especially 6 to 12, for particularcompounds within the polyethyleneamine mixture. When R is ethylene amineor polyethyleneamine, the value of x+y is preferably such that theparticular compounds within the polyethyleneamine mixture contain 3 to17, especially 6 to 12, nitrogen atoms.

Suitable polyethyleneamine mixtures are available commercially. Anexample of such a commercially available material is sold by The DowChemical Company as Heavy Polyamine X. That material has a numberaverage molecular weight of 275 g/mol.

The alkali metal, ammonium or phosphonium sulfite includes compoundshaving the formula A₂SO₃, where A represents alkali metal, ammonium orphosphonium, and alkali metal, ammonium or phosphonium hydrogen sulfite(alkali metal, ammonium or phosphonium bisulfite) compounds having theformula AHSO₃, where A is as before. Examples of such compounds include,for example, dilithium sulfite, disodium sulfite, dipotassium sulfite,di(tetramethyl ammonium) sulfite, di(tetramethyl phosphonium) sulfite,lithium hydrogen sulfite (LiHSO₃), sodium hydrogen sulfite (NaHSO₃),potassium hydrogen sulfite (KHSO₃), cesium hydrogen sulfite (CsHSO₃),(tetramethyl ammonium) hydrogen sulfite, (tetramethyl phosphonium)hydrogen sulfite, with the sodium compounds being preferred among these.A suitable amount of alkali metal, ammonium or phosphonium sulfite isfrom 0.01 to 5 pph. The amount of alkali metal, ammonium or phosphoniumsulfite may be at least 0.02 pph, at least 0.025 pph or at least 0.05pph and may be up to 2 pph, up to 1 pph, up to 0.5 pph, up to 0.25 pphor up to 0.2 pph.

The foam formulation includes at least one isocyanate-reactive compoundthat has a functionality of at least 2 and an equivalent weight of atleast 200 per isocyanate-reactive group. “Functionality” refers to theaverage number of isocyanate-reactive groups per molecule. Thefunctionality may be as much as 8 or more but preferably is from 2 to 4.The isocyanate groups may be, for example, hydroxyl, primary amino orsecondary amino groups, but hydroxyl groups are preferred. Theequivalent weight may be up to 6000 or more, but is preferably from 500to 3000 and more preferably from 1000 to 2000. This isocyanate-reactivecompound may be, for example, a polyether polyol, a polyester polyol, ahydroxyl-terminated butadiene polymer or copolymer, ahydroxyl-containing acrylate polymer, and the like. A preferred type ofisocyanate-reactive compound is a polyether polyol, especially a polymerof propylene oxide or a copolymer of propylene oxide and ethylene oxide.A copolymer of propylene oxide and ethylene oxide may be a blockcopolymer having terminal poly(oxyethylene) blocks and in which at least50% of the hydroxyl groups are primary. Another suitable copolymer ofpropylene oxide and ethylene oxide may be a random or pseudo-randomcopolymer, which may also contain terminal poly(oxyethylene) blocks andin which at least 50% of the hydroxyl groups are primary.

Polyester polyols that are useful as the isocyanate-reactive compoundinclude reaction products of polyols, preferably diols, withpolycarboxylic acids or their anhydrides, preferably dicarboxylic acidsor dicarboxylic acid anhydrides. The polycarboxylic acids or anhydridesmay be aliphatic, cycloaliphatic, aromatic and/or heterocyclic and maybe substituted, such as with halogen atoms. The polycarboxylic acids maybe unsaturated. Examples of these polycarboxylic acids include succinicacid, adipic acid, terephthalic acid, isophthalic acid, trimelliticanhydride, phthalic anhydride, maleic acid, maleic acid anhydride andfumaric acid. The polyols used in making the polyester polyolspreferably have an equivalent weight of about 150 or less and includeethylene glycol, 1,2- and 1,3-propylene glycol, 1,4- and 1,3-butanediol, 1,6-hexane diol, 1,8-octane diol, neopentyl glycol, cyclohexanedimethanol, 2-methyl-1,3-propane diol, glycerine, trimethylolpropane,1,2,6-hexane triol, 1,2,4-butane triol, trimethylolethane,pentaerythritol, quinitol, mannitol, sorbitol, methyl glycoside,diethylene glycol, triethylene glycol, tetraethylene glycol, dipropyleneglycol, dibutylene glycol and the like. Polycaprolactone polyols such asthose sold by The Dow Chemical Company under the trade name “Tone” arealso useful.

Mixtures of two or more of the foregoing isocyanate-reactive compoundshaving a functionality of at least 2 and an equivalent weight of atleast 200 per isocyanate-reactive group can be used if desired.

The isocyanate-reactive compound(s) may contain dispersed polymerparticles. These so-called polymer polyols contain, for example,particles of vinyl polymers such as styrene, acrylonitrile orstyrene-acrylonitrile, particles of a polyurea polymer, or polymers of apolyurethane-urea polymer.

In addition, such isocyanate-reactive compounds can be used in admixturewith one or more crosslinkers and/or chain extenders. For purposes ofthis specification, “crosslinkers” are compounds having at least threeisocyanate-reactive groups per molecule and an equivalent weight perisocyanate-reactive group of below 200. “Chain extenders” for purposesof this invention have exactly two isocyanate-reactive groups permolecule and have an equivalent weight per isocyanate-reactive group ofbelow 200. In each case, the isocyanate-reactive groups are preferablyhydroxyl, primary amino or secondary amino groups. Crosslinkers andchain extenders preferably have equivalent weights of up to 150 and morepreferably up to about 125.

Examples of crosslinkers include glycerin, trimethylolpropane,trimethylolethane, diethanolamine, triethanolamine, triisopropanolamine,alkoxylates of any of the foregoing that have equivalent weights of upto 199, and the like. Examples of chain extenders include alkyleneglycols (e.g., ethylene glycol, propylene glycol, 1,4-butane diol,1,6-hexanediol and the like), glycol ethers (such as diethylene glycol,triethylene glycol, dipropylene glycol, tripropylene glycol and thelike), ethylene diamine, toluene diamine, diethyltoluene diamine and thelike, as well as alkoxylates of any of the foregoing that haveequivalent weights of up to 199, and the like.

Crosslinkers and/or chain extenders are typically present in smallamounts (if at all). A preferred amount is from 0 to 5 pph ofcrosslinkers and/or chain extenders. A more preferred amount is from0.05 to 2 pph and a still more preferred amount is from 0.1 to 1 pph ofone or more crosslinkers.

Examples of suitable polyisocyanates include, for example, m-phenylenediisocyanate, 2,4- and/or 2,6-toluene diisocyanate (TDI), the variousisomers of diphenylmethanediisocyanate (MDI), the so-called polymericMDI products (which are a mixture of polymethylene polyphenylenepolyisocyanates in monomeric MDI), carbodiimide-modified MDI products(such as the so-called “liquid MDI” products which have an isocyanateequivalent weight in the range of 135-170),hexamethylene-1,6-diisocyanate, tetramethylene-1,4-diisocyanate,cyclohexane-1,4-diisocyanate, hexahydrotoluene diisocyanate,hydrogenated MDI (H₁₂MDI), isophorone diisocyanate,naphthylene-1,5-diisocyanate, methoxyphenyl-2,4-diisocyanate,4,4′-biphenylene diisocyanate, 3,3′-dimethyoxy-4,4′-biphenyldiisocyanate, 3,3′-dimethyldiphenyl methane-4,4′-diisocyanate,4,4′,4″-triphenylmethane diisocyanate, hydrogenated polymethylenepolyphenylpolyisocyanates, toluene-2,4,6-triisocyanate and4,4′-dimethyldiphenylmethane-2,2′,5,5′-tetraisocyanate. Any of theforegoing that is modified to contain urethane, urea, uretonimine,biuret, allophonate and/or carbodiimide groups may be used.

Preferred isocyanates include TDI, MDI and/or polymeric MDI, as well asderivatives of MDI and/or polymeric MDI that contain urethane, urea,uretonimine, biuret, allophonate and/or carbodiimide groups. Anespecially preferred isocyanate is a mixture of TDI and MDI.

The amount of polyisocyanate provided to the foam formulation isexpressed as the “isocyanate index”, which is 100 times the ratio ofisocyanate groups to isocyanate-reactive groups in the foam formulation.The isocyanate index is typically from about 70 to 150. A preferredisocyanate index is from 80 to 125 and a more preferred isocyanate indexis from 80 to 115. In some embodiments, the isocyanate index is from 90to 115 or from 95 to 115.

The blowing agent may be a chemical (exothermic) type, a physical(endothermic) type or a mixture of at least one of each type. Chemicaltypes typically react or decompose to produce carbon dioxide or nitrogengas under the conditions of the foaming reaction. Water and variouscarbamate compounds are examples of suitable chemical blowing agents.Physical types include carbon dioxide, various low-boiling hydrocarbons,hydrofluorocarbons, hydroflurochlorocarbons, ethers and the like. Wateris most preferred blowing agent, either by itself or in combination withone or more physical blowing agents.

Blowing agents are present in amounts sufficient to provide the desiredfoam density. When water is the blowing agent, a suitable amount isgenerally from 1.5 to 6 pph, preferably from 2 to 5 pph.

Suitable surfactants are materials that help to stabilize the cells ofthe foaming reaction mixture until the materials have cured. A widevariety of silicone surfactants as are commonly used in makingpolyurethane foams can be used in making the foams with the polymerpolyols or dispersions of this invention. Examples of such siliconesurfactants are commercially available under the tradenames Tegostab™(Evonik Corporation), Niax™ (Momentive) and Dabco™ (Air Products andChemicals).

Surfactants are typically present in amounts up to 5 pph, more typicallyfrom 0.1 to 2 pph and preferably from 0.25 to 1.5 pph.

Suitable catalysts include those described by U.S. Pat. No. 4,390,645,which is incorporated herein by reference. Representative catalystsinclude:

(a) tertiary amines, such as trimethylamine, triethylamine,N-methylmorpholine, N-ethylmorpholine, N,N-dimethylbenzylamine,N,N-dimethylethanolamine, N,N,N′,N′-tetramethyl-1,4-butanediamine,N,N-dimethylpiperazine, 1,4-diazobicyclo-2,2,2-octane,bis(dimethylaminoethyl)ether, bis(2-dimethylaminoethyl) ether,morpholine,4,4′-(oxydi-2,1-ethanediyl)bis,tri(dimethylaminopropyl)amine, pentamethyldiethylenetriamine andtriethylenediamine and the like; as well as so-called “low emissive”tertiary amine catalysts that contain one or more isocyanate-reactivegroups such as dimethylaminepropylamine and the like;(b) tertiary phosphines, such as trialkylphosphines anddialkylbenzylphosphines;(c) chelates of various metals, such as those which can be obtained fromacetylacetone, benzoylacetone, trifluoroacetyl acetone, ethylacetoacetate and the like with metals such as Be, Mg, Zn, Cd, Pd, Ti,Zr, Sn, As, Bi, Cr, Mo, Mn, Fe, Co and Ni;(d) acidic metal salts of strong acids, such as ferric chloride, stannicchloride, stannous chloride, antimony trichloride, bismuth nitrate andbismuth chloride;(e) strong bases, such as alkali and alkaline earth metal hydroxides,alkoxides and phenoxides;(f) alcoholates and phenolates of various metals, such as Ti(OR)₄,Sn(OR)₄ and Al(OR)_(a), wherein R is alkyl or aryl, and the reactionproducts of the alcoholates with carboxylic acids, beta-diketones and2-(N,N-dialkylamino)alcohols;(g) salts of organic acids with a variety of metals, such as alkalimetals, alkaline earth metals, Al, Sn, Pb, Mn, Co, Ni and Cu including,for example, sodium acetate, stannous octoate, stannous oleate, leadoctoate, metallic driers, such as manganese and cobalt naphthenate; and(h) organometallic derivatives of tetravalent tin, trivalent andpentavalent As, Sb and Bi and metal carbonyls of iron and cobalt.

Catalysts are typically present in small amounts, such as up to 2 pphand generally up to 1 pph. A preferred amount of catalyst is from 0.05to 1 pph.

It is preferred to produce the foam in the presence of at least oneantioxidant. Such an antioxidant may be blended with the isocyanatereactive compound(s) that have at least two isocyanate-reactive groupsper molecule and an equivalent weight of at least 200 perisocyanate-reactive group prior to forming the polyurethane foam, in themanner described above with regard to the polyethyleneamine mixturehaving a number average molecular weight of 175 to 450. Alternatively,it may be added into the reaction mixture with one or more otheringredients and/or as a separate ingredient or stream.

Examples of suitable antioxidants include, for example:

1) Phenolic compounds such as 2,6-di-tert-butyl-4-methylphenol,2-tert-butyl-4,6-dimethylphenol, 2,6-di-tert-butyl-4-ethylphenol,2,6-di-tert-butyl-4-n-butylphenol, 2,6-di-tert-butyl-4-isobutylphenol,2,6-dicyclopentyl-4-methylphenol,2-(α-methylcyclohexyl)-4,6-dimethylphenol,2,6-dioctadecyl-4-methylphenol, 2,4,6-tricyclohexylphenol,2,6-di-tert-butyl-4-methoxymethylphenol, nonylphenols which are linearor branched in the side chains, for example 2,6-di-nonyl-4-methylphenol,2,4-dimethyl-6-(1′-methylundec-1′-yl)phenol,2,4-dimethyl-6-(1′-methylheptadec-1′-yl)phenol,2,4-dimethyl-6-(1′-methyltridec-1′-yl)phenol,2,4-dioctylthiomethyl-6-tert-butylphenol, 2,4-dioctylthiomethylmethylphenol, 2,4-dioctylthiomethyl-6-ethylphenol,2,6-di-dodecylthiomethyl-4-nonylphenol,2,6-di-tert-butyl-4-methoxyphenol, 2,5-di-tert-butylhydroquinone,2,5-di-tert-amylhydroquinone, 2,6-diphenyl-4-octadecyloxyphenol,2,6-di-tert-butylhydroquinone, 2,5-di-tert-butyl-4-hydroxyanisole,3,5-di-tert-butyl-4-hydroxyanisole, 3,5-di-tert-butyl-4-hydroxyphenylstearate, bis(3,5-di-tert-butyl-4-hydroxyphenyl) adipate,2,2′-methylenebis(6-tert-butyl-4-methylphenol),2,2′-methylenebis(6-tert-butyl-4-ethylphenol),2,2′-methylenebis[4-methyl-6-(α-methylcyclohexyl)phenol],2,2′-methylenebis(4-methyl-6-cyclohexylphenol),2,2′-methylenebis(6-nonyl-4-methylphenol),2,2′-methylenebis(4,6-di-tert-butylphenol),2,2′-ethylidenebis(4,6-di-tert-butylphenol),2,2′-ethylidenebis(6-tert-butyl-4-isobutylphenol),2,2′-methylenebis[6-(α-methylbenzyl)-4-nonylphenol],2,2′-methylenebis[6-(α,α-dimethylbenzyl)-4-nonylphenol],4,4′-methylenebis(2,6-di-tert-butylphenol),4,4′-methylenebis(6-tert-butyl-2-methylphenol),1,1-bis(5-tert-butyl-4-hydroxy-2-methylphenyl)butane,2,6-bis(3-tert-butyl-5-methyl-2-hydroxybenzyl)-4-methylphenol,1,1,3-tris(5-tert-butyl-4-hydroxy-2-methylphenyl)butane,1,1-bis(5-tert-butyl-4-hydroxy-2-methylphenyl)-3-n-dodecylmercaptobutane,ethylene glycol bis[3,3-bis(3′-tert-butyl-4′-hydroxyphenyl)butyrate],bis(3-tert-butyl-4-hydroxy-5-methyl-phenyl)dicyclopentadiene,bis[2-(3′-tert-butyl-2′-hydroxy-5′-methylbenzyl)-6-tert-butyl-4-methylphenyl]terephthalate,1,1-bis-(3,5-dimethyl-2-hydroxyphenyl)butane,2,2-bis(3,5-di-tert-butyl-4-hydroxyphenyl)propane,2,2-bis-(5-tert-butyl-4-hydroxy2-methylphenyl)-4-n-dodecylmercaptobutane,1,1,5,5-tetra(5-tert-butyl-4-hydroxy-2-methylphenyl)pentane,1,3,5-tris(3,5-di-tert-butyl-4-hydroxybenzyl)-2,4,6-trimethylbenzene,1,4-bis(3,5-di-tert-butyl-4-hydroxybenzyl)-2,3,5,6-tetramethylbenzene,2,4,6-tris(3,5-di-tert-butyl-4-hydroxybenzyl)phenol, esters ofβ-(3,5-di-tert-butyl-4-hydroxyphenyl)propionic acid with mono- orpolyhydric alcohols, e.g. with methanol, ethanol, n-octanol, i-octanol,octadecanol, 1,6-hexanediol, 1,9-nonanediol, ethylene glycol,1,2-propanediol, neopentyl glycol, thiodiethylene glycol, diethyleneglycol, triethylene glycol, pentaerythritol,tris(hydroxyethyl)isocyanurate, N,N′-bis(hydroxyethyl)oxamide,3-thiaundecanol, 3-thiapentadecanol, trimethylhexanediol,trimethylolpropane,4-hydroxymethyl-1-phospha-2,6,7-trioxabicyclo[2.2.2]octane, esters ofβ-(5-tert-butyl-4-hydroxy-3-methylphenyl)propionic acid with mono- orpolyhydric alcohols, e.g. with methanol, ethanol, n-octanol, i-octanol,octadecanol, 1,6-hexanediol, 1,9-nonanediol, ethylene glycol,1,2-propanediol, neopentyl glycol, thiodiethylene glycol, diethyleneglycol, triethylene glycol, pentaerythritol,tris(hydroxyethyl)isocyanurate, N,N′-bis(hydroxyethyl)oxamide,3-thiaundecanol, 3-thiapentadecanol, trimethylhexanediol,trimethylolpropane,4-hydroxymethyl-1-phospha-2,6,7-trioxabicyclo[2.2.2]octane;3,9-bis[2-{3-(3-tert-butyl-4-hydroxy-5-methylphenyl)propionyloxy}-1,1-dimethylethyl]-2,4,8,10-tetraoxaspiro[5.5]-undecane,esters of β-(3,5-dicyclohexyl-4-hydroxyphenyl)propionic acid with mono-or polyhydric alcohols, e.g. with methanol, ethanol, octanol,octadecanol, 1,6-hexanediol, 1,9-nonanediol, ethylene glycol,1,2-propanediol, neopentyl glycol, thiodiethylene glycol, diethyleneglycol, triethylene glycol, pentaerythritol,tris(hydroxyethyl)isocyanurate, N,N′-bis(hydroxyethyl)oxamide,3-thiaundecanol, 3-thiapentadecanol, trimethylhexanediol,trimethylolpropane,4-hydroxymethyl-1-phospha-2,6,7-trioxabicyclo[2.2.2]octane, esters of3,5-di-tert-butyl-4-hydroxyphenyl acetic acid with mono- or polyhydricalcohols, e.g. with methanol, ethanol, octanol, octadecanol,1,6-hexanediol, 1,9-nonanediol, ethylene glycol, 1,2-propanediol,neopentyl glycol, thiodiethylene glycol, diethylene glycol, triethyleneglycol, pentaerythritol, tris(hydroxyethyl)isocyanurate,N,N′-bis(hydroxyethyl)oxamide, 3-thiaundecanol, 3-thiapentadecanol,trimethylhexanediol, trimethylolpropane,4-hydroxymethyl-1-phospha-2,6,7-trioxabicyclo[2.2.2]octane;2) Aminic antioxidants such as N,N′-di-isopropyl-p-phenylenediamine,N,N′-di-sec-butyl-p-phenylenediamine,N,N′-bis(1,4-dimethylpentyl)-p-phenylenediamine,N,N′-bis(1-ethyl-3methylpentyl)-p-phenylenediamine,N,N′-bis(1-methylheptyl)-p-phenylenediamine,N,N′-dicyclohexyl-p-phenylenediamine, N,N′-diphenyl-p-phenylenediamine,N,N′-bis(2-naphthyl)-p-phenylenediamine,N-isopropyl-N′-phenyl-p-phenylenediamine,N-(1,3-dimethylbutyl)-N′-phenyl-p-phenylenediamine,N-(1-methylheptyl)-N′-phenyl-p-phenylenediamine,N-cyclohexyl-N′-phenyl-p-phenylenediamine,4-(p-toluenesulfamoyl)diphenylamine,N,N′-dimethyl-N,N′-di-sec-butyl-p-phenylenediamine, diphenylamine,N-allyldiphenylamine, 4-isopropoxydiphenylamine,N-phenyl-1-naphthylamine, N-(4-tert-octylphenyl)-1-naphthylamine,N-phenyl-2-naphthylamine, octylated diphenylamine, for examplep,p′-di-tert-octyldiphenylamine, 4-n-butyl-aminophenol,4-butyrylaminophenol, 4-nonanoylaminophenol, 4-dodecanoylaminophenol,4-octadecanoylaminophenol, bis(4-methoxyphenyl)amine,2,6-di-tert-butyl-4-dimethylaminomethylphenol,2,4′-diaminodiphenylmethane, 4,4′-diaminodiphenylmethane,N,N,N′,N′-tetra-methyl-4,4′-diaminodiphenylmethane,1,2-bis[(2-methylphenyl)amino]ethane, 1,2-bis(phenylamino)propane,(o-tolyl)biguanide, bis[4-(1′,3′-dimethylbutyl)phenyl]amine,tert-octylated N-phenyl-1-naphthylamine, a mixture of mono- anddialkylated tert-butyl/tert-octyldiphenylamines, a mixture of mono- anddialkylated nonyldiphenylamines, a mixture of mono- and dialkylateddodecyldiphenylamines, a mixture of mono- and dialkylatedisopropyl/isohexyldiphenylamines, a mixture of mono- and dialkylatedtert-butyldiphenylamines, and the like;3) Thiosynergists such as dilauryl thiodipropionate or distearylthiodipropionate;4) Phosphites and phosphonites such as triphenyl phosphite,diphenylalkyl phosphites, phenyldialkyl phosphites, tris(nonylphenyl)phosphite, trilauryl phosphite, trioctadecyl phosphite,distearylpentaerythritol diphosphite, tris(2,4-di-tert-butylphenyl)phosphite, diisodecyl pentaerythritol diphosphite,bis(2,4-di-tert-butylphenyl)pentaerythritol diphosphite,bis(2,4-di-cumylphenyl)pentaerythritol diphosphite,bis(2,6-di-tert-butyl-4-methylphenyl)pentaerythritol diphosphite,diisodecyloxypentaerythritol diphosphite,bis(2,4-di-tert-butyl-6-methylphenyl)pentaerythritol diphosphite,bis(2,4,6-tris(tert-butylphenyl)pentaerythritol diphosphite, tristearylsorbitol triphosphite, tetrakis(2,4-di-tert-butylphenyl)4,4′-biphenylene diphosphonite,6-isooctyloxy-2,4,8,10-tetra-tert-butyl-12H-dibenz[d,g]-1,3,2-dioxaphosphocin,bis(2,4-di-tert-butyl-6-methylphenyl)methyl phosphite,bis(2,4-di-tert-butyl-6-methylphenyl)ethyl phosphite,6-fluoro-2,4,8,10-tetra-tert-butyl-12-methyl-dibenz[d,g]-1,3,2-dioxaphosphocin,2,2′,2″-nitrilo-[triethyltris(3,3′,5,5′-tetra-tert-butyl-1,1′-biphenyl-2,2′-diyl)phosphite],2-ethylhexyl(3,3′,5,5′-tetra-tert-butyl-1,1′-biphenyl-2,2′-diyl)phosphite,5-butyl-5-ethyl-2-(2,4,6-tri-tert-butylphenoxy)-1,3,2-dioxaphosphirane;5) Benzofuranones and indolinones such as those disclosed in U.S. Pat.Nos. 4,325,863; 4,338,244; 5,175,312; 5,216,052; 5,252,643;DE-A-4316611; DE-A-4316622; DE-A-4316876; EP-A-0589839 or EP-A-0591102,including for example3-[4-(2-acetoxyethoxy)phenyl]-5,7-di-tert-butylbenzofuran-2-one,5,7-di-tert-butyl-3-[4-(2-stearoyloxyethoxy)phenyl]-benzofuran-2-one,3,3′-bis[5,7-di-tert-butyl-3-(4-[2-hydroxyethoxy]phenyl)benzofuran-2-one],5,7-di-tert-butyl-3-(4-ethoxyphenyl)benzofuran-2-one,3-(4-acetoxy-3,5-dimethylphenyl)-5,7-di-tert-butylbenzofuran-2-one,3-(3,5-dimethyl-4-pivaloyloxyphenyl)-5,7-di-tert-butylbenzofuran-2-one,3-(3,4-dimethylphenyl)-5,7-di-tert-butylbenzofuran-2-one,3-(2,3-dimethylphenyl)-5,7-di-tert-burylbenzofuran-2-one, as well as6) tocophenols, hydroxylated thiodiphenyl ethers, O-, N- and S-benzylcompounds, hydroxybenzylated malonates, triazine compounds,benzylphosphonates, acylaminophenols, amides ofβ-(3,5-di-tert-butyl-4-hydroxyphenyl)propionic acid, ascorbic acid(vitamin C), 2-(2′-hydroxyphenyl)benzotriazoles, 2-hydroxybenzophenones,esters of substituted and unsubstituted benzoic acids, acrylates, nickelcompounds, oxamides, 2-(2-hydroxyphenyl)-1,3,5-triazines,hydroxylamines, nitrones, esters of β-thiodipropionic acid, asdescribed, for example, in U.S. Pat. No. 6,881,774, incorporated hereinby reference.

Preferred antioxidants include:

a) mixtures of at least one phenolic compound as described in 1) abovewith at least one phosphite or phosphonite compound as described in 4)above;

b) mixtures of at least one phenolic compound as described in 1) abovewith at least one benzofuranone or indolinone compound as described in5) above;

c) mixtures of at least one phenolic compound as described in 1) abovewith at least one aminic antioxidant as described in 2) above;

d) mixtures of at least one phenolic compound as described in 1) abovewith at least one phosphite or phosphonite compound as described in 4)above and at least one benzofuranone or indolinone compound as describedin 5) above;

e) mixtures of at least one phenolic compound as described in 1) abovewith at least one phosphite or phosphonite compound as described in 4)above and at least one aminic compound as described in 2) above;

f) mixtures of at least one phenolic compound as described in 1) abovewith at least one phosphite or phosphonite compound as described in 4)above, at least one benzofuranone or indolinone compound as described in5) above and at least one aminic compound as described in 2) above;g) mixtures of at least one phenolic compound as described in 1) abovewith at least one thiosynergist as described in 3); andh) any of mixtures a)-f) above with at least one thiosynergist asdescribed in 3).

The antioxidant(s), when used, is present in an effective amount, suchas up to about 10 pph. A preferred amount is from 0.1 to 5 pph, and amore preferred amount is from 0.2 to 1.5 pph.

In some embodiments, a HALS (hindered amine light stabilizer) compoundis present. Suitable HALS compounds includebis(1-octyloxy)-2,2,5,5-tetramethyl-4-piperidinyl) sebacate (Tinuvin™123 from BASF),n-butyl-(3,5-di-tert-butyl-4-hydroxylbenzyl)bis-(1,2,2,6-pentamethyl-4-piperidinyl)malonate(Tinuvin™ 144 from BASF), dimethyl succinate polymer with4-hydroxy-2-2,6,6-tetramethyl-1-piperidinethanol (Tinuvin™ 622 fromBASF), bis(1,2,2,6,6-pentamethyl-4-piperidinyl) sebacate (Tinuvin™ 765from BASF) and bis(2,2,6,6-tetramethyl-4-piperidinyl) sebacate (Tinuvin™770 from BASF) and the like.

The HALS compound, when used, is present in an effective amount, such asup to about 10 pph in the aggregate. A preferred amount is from 0.1 to 5pph in the aggregate, and a more preferred amount is from 0.1 to 2.5pph.

Other ingredients may be present during the foaming step, including, forexample, fillers, colorants, odor masks, flame retardants, biocides,antistatic agents, thixotropic agents and cell openers.

Polyurethane foam is made in accordance with this invention by forming areaction mixture containing the various ingredients and curing thereaction mixture. Free-rise processes such as continuous slabstockproduction methods can be used. Alternatively, molding methods can beused. Such processes are well known. Generally, no alternation ofconventional processing operations is needed to produce polyurethanefoam in accordance with this invention (other than the inclusion of thepolyethyleneamine mixture having a number average molecular weight of175 to 450 and alkali metal, ammonium or phosphonium sulfite andoptionally the antioxidant(s) and/or HALS compound).

The various ingredients may be introduced individually or in varioussubcombinations into a mixhead or other mixing device where they aremixed and dispensed into a region (such as a trough or other opencontainer, or a closed mold) where they are cured. It is oftenconvenient, especially when making molded foam, to form a formulatedpolyol component that contains the isocyanate-reactive compound(s),including crosslinkers and/or chain extenders as may be used, thepolyethyleneamine mixture having a number average molecular weight of175 to 450, alkali metal, ammonium or phosphonium sulfite, theantioxidant(s) and HALS compounds (if any), and optionally thecatalyst(s), surfactant(s) and blowing agent(s). This formulated polyolcomponent is then contacted with the polyisocyanate (as well as anyother ingredients that are not present in the formulated polyolcomponent) to produce the foam.

Some or all of the various components may be heated prior to mixing themto form the reaction mixture. In other cases, the components are mixedat approximately ambient temperatures (such as from 15-40° C.). Heat maybe applied to the reaction mixture after all ingredients have beenmixed, but this is often unnecessary.

The product of the curing reaction is a flexible polyurethane foam. Thefoam density may be from 20 to 200 kg/m³. For most seating and beddingapplications, a preferred density is from 24 to 80 kg/m³. The foam mayhave a resiliency of at least 50% on the ball rebound test of ASTM3574-H. Foams produced in accordance with this invention are useful, forexample, in cushioning applications such as bedding and domestic, officeor vehicular seating, as well as in other vehicular applications such asheadrests, dashboards instrument panels, armrests or headliners.

Polyurethane foams made in accordance with the invention arecharacterized in having reduced emissions formaldehyde, acetaldehyde,acrolein and propionaldehyde compared to the case in which thepolyethyleneamine mixture having a number average molecular weight of175 to 450 and alkali metal, ammonium or phosphonium sulfite are absent.A suitable method for measuring formaldehyde, acetaldehyde, acrolein andpropionaldehyde emissions is as follows: The polyurethane foam sample iscrushed to open the cells. The crushed foam is cut into cubic 30 gramsamples, which are immediately packaged tightly in aluminum foil orpolyethylene film and kept in this manner for 5 days at about 25° C.

Aldehyde concentrations are measured according to the Toyota TSM0508Gtest method. In that Toyota method, the foam sample is removed from thefoil or film and placed in individual 10 L Tedlar gas bags (Delin Co.,Ltd., China) that has previously been purged three times with nitrogengas. The bag with the foam sample is filled with 7 L of nitrogen, sealedand heated 65° C. for two hours. The plastic bag containing the foams isremoved from the oven. The gas in the bag is pumped through a 350 mgdinitrophenylhydrazine cartridge to capture the carbonyl compounds. Thecaptured carbonyl compounds are analyzed for formaldehyde, acetaldehyde,acrolein and propionaldehyde by liquid chromatography. Details for aspecific method of performing the Toyota method are described in thefollowing examples.

The amount of emitted formaldehyde, acetaldehyde, acrolein andpropionaldehyde as determined by this method are all typically at least20%, usually at least 50%, and sometimes as much as 80 to 98%, reducedas compared to an otherwise like foam that is produced in the absence ofthe polyethyleneamine mixture having a number average molecular weightof 175 to 450 and alkali metal, ammonium or phosphonium sulfite. Anadvantage of this invention is that significant reductions are seen inthe emitted amounts of all four of these aldehyde compounds.

In some embodiments, the amount of emitted formaldehyde and amount ofemitted acrolein each are no greater than 10 μg/m³ or no greater than 5μg/m³, as measured according to the Toyota method. In some embodiments,the amount of emitted acetaldehyde is no greater than 100 μg/m³, nogreater than 50 μg/m³, or no greater than 35 μg/m³, as measuredaccording to Toyota method. In some embodiments, the amount of emittedpropionaldehyde is no greater than 60 μg/m³ or no greater than 50 μg/m³,as measured according to the Toyota method. The sum of emitted amountsof formaldehyde, acetaldehyde, acrolein and propionaldehyde in someembodiments is no greater than 150 μg/m³, no greater than 100 μg/m³, nogreater than 75 μg/m³ or no greater than 50 μg/m³, as measured accordingto the Toyota method.

The following examples are provided to illustrate the invention, but arenot intended to limit the scope thereof. All parts and percentages areby weight unless otherwise indicated.

EXAMPLE 1 AND COMPARATIVE SAMPLES A AND B

Formulated Polyol A is made by combining 45.34 parts of aglycerin-initiated poly(propylene oxide) capped with 15 percent ethyleneoxide and having a hydroxyl number of 27.5 mg KOH/g; 50.11 parts of acopolymer polyol having a hydroxyl number of 22 mg KOH/g and containing40 percent by weight copolymerized styrene and acrylonitrile solidsdispersed in a polyether polyol; 0.48 part of diethanolamine, 0.38 partof glycerine, 0.27 part of a 33 percent triethylene diamine indipropylene glycol, 0.17 part of a tertiary amine/glycol mixtureavailable as C225 from Momentive Co., Ltd.; 1.15 parts of anorganosilicone foam-stabilizing surfactant, 2.1 parts of water and 0.5part of benzenepropanoic acid, 3,5-bis(1,1-dimethyl-ethyl)-4-hydroxy-C7-C9 branched alkyl esters (available asIRGANOX™ 1135 antioxidant from BASF (China) Co., Ltd).

Formulated Polyol B is made by combining 100.5 parts of FormulatedPolyol A with 0.1 part of a polyethyleneimine having a number averagemolecular weight of about 600 in a high speed laboratory mixer.

Formulated Polyol C is made by combining 100.5 parts of FormulatedPolyol A with 0.1 part of a polyethyleneimine having a number averagemolecular weight of about 600 and 0.1 part of sodium hydrogen sulfite(NaHSO₃) in a high speed laboratory mixer.

Formulated Polyol 1 is made by combining 100.5 parts of FormulatedPolyol A with 0.1 part of a polyethyleneamine having a number averagemolecular weight of about 275 (Heavy Polyamine X from The Dow ChemicalCompany) and 0.1 part of sodium hydrogen sulfite (NaHSO₃) in a highspeed laboratory mixer.

Each of Formulated Polyols A-C and 1 are stored at room temperature for12-24 hours before being processed into a foam.

Comparative Sample A is made by combining 100 parts of Formulated PolyolA with 28 parts of a 20/80 by weight blend of toluene diisocyanate (TDI)and methylene diphenyldiisocyanate (MDI), pouring the resulting reactionmixture into a cup and allowing the reaction mixture to rise and cure toform a polyurethane foam. After the foam has cured enough to bedimensionally stable, it is removed from the cup and 30 gram samplecubes are cut. The foam cubes each are immediately wrapped in aluminumfoil to form an airtight package for 7 days.

Comparative Sample B is made in the same manner, except 100 parts ofFormulated Polyol B are combined with 28 parts of the same TDI/MDIblend.

Comparative Sample C is made in the same manner, except 100 parts ofFormulated Polyol B are combined with 28 parts of the same TDI/MDIblend.

Example 1 is made in the same manner, except 101 parts of FormulatedPolyol 1 are combined with 28 parts of the same TDI/MDI blend.

Aldehydes emitted from the foam samples are analyzed using the Toyotagas bag method. The cubed foam samples are in each case removed from thefoil and put into a 10 L Tedlar gas bag that has been washed with purenitrogen three times and emptied. An empty gas bag is used as a blank.After the foam sample is put into the gas bag, the bag is filled withabout 7 L of nitrogen gas and heated in the oven for 2 hours at 65° C.The nitrogen gas in the gas bag is then pumped out by an air pump andanalyzed for formaldehyde, acetaldehyde, acrolein (propenyl aldehyde)and propionaldehyde.

The gas from each bag is passed through a dinitrophenylhydrazine (DNPH)cartridge (CNWBOND DNPH-Silica cartridge, 350 mg, Cat. No. SEEQ-144102,Anple Co., Ltd.) at a sampling speed is 330 mL/min. The aldehydesemitted from the foam into the gas are absorbed by the cartridge to formDNPH derivatives. The DNPH cartridge is eluted with 3 g of acetonitrile,and the resulting acetonitrile solution is analyzed by HPLC to quantifythe carbonyls in the sample, as follows.

A standard solution containing 15 μg/mL each of formaldehyde,acetaldehyde, acrolein and propionaldehyde (in each case in the form ofDNPH derivatives) (TO11A carbonyl-DNPH mix, Cat. No. 48149-U, SupelcoCo., Ltd) is diluted with acetonitrile. A vial containing 2 mL of thediluted solution (containing 0.794 ppm of each of formaldehyde,acetaldehyde, acrolein and propionaldehyde) is refrigerated to −4° C.The refrigerated solution is injected into the HPLC system and analyzedfor formaldehyde, acetaldehyde, acrolein and propionaldehydederivatives. The response factor is calculated from the area of theelution peak for each derivative, according the formula:

${{Response}{factor}i} = \frac{{Peak}{Area}i}{0.794}$where Response factor i=Response factor of derivative i; Peak Areai=Peak Area of derivative i in standard solution and 0.794=theconcentration of each derivative in the standard solution.

The amounts of formaldehyde, acetaldehyde, acrolein and propionaldehydeemitted by each of Comparative Samples A and B and Example 1 are thendetermined. In each case, the acetonitrile solution obtained by elutingthe DNPH column is injected into the HPLC system and the area of theelution peak is determined from each derivative. The concentration ofthe aldehyde-DNPH derivative in the sample solution is calculated asfollows:

${{Concentration}{of}i} = \frac{{Peak}{Area}i}{{Response}{factor}{}i}$where: Concentration of i=Concentration of aldehyde-DNPH derivative inthe sample solution, Peak Area i=Peak Area of Derivative i in samplesolution and Response factor i=Response factor of derivative i,determined from the standard solutions as described above.

The HPLC conditions are as follows:

Instrument: Agilent 1200 HPLC Column: Supelco Ascentis Express C18, 15cm*4.6 mm, 2.7 um Mobile Phase: Solvent A: 0.1% H₃PO₄ in AcetonitrileSolvent B: 0.1% H₃PO₄ in DI water Column Oven: 15° C. Detection: DADdetector at 360 nm Gradient: Time (mn) % A % B Flow (mL/min)  0  45 55 1 7  45 55 1 14  50 50 1 20  85 15 1 25 100  0 1 Equilibration Time: 5min Injection: 10 uL

The concentrations of formaldehyde, acetaldehyde, acrolein andpropionaldehyde for each of Comparative Samples A and B and Example 1are as indicated in Table 1.

TABLE 1 Comp. A* Comp. B* Comp. C* Ex. 1 Additives 0.5% 0.5% 0.5% 0.5%IRGANOX IRGANOX IRGANOX IRGANOX 1135 1135 1135 1135 0.1% 600 0.1% 6000.1% 275 MW MW PEI MW PEI² polyethylene- 0.1% amine 0.1% NaHSO₃ NaHSO₃Formaldehyde,  9-13¹  13  3  0 μg/m³ Acetaldehyde, 111-115¹ 142  29  20μg/m³ Acrolein, μg/m³ 24-25¹  23  0  0 Propionaldehyde, 238-258¹ 167 103 87 μg/m³ Total Aldehydes, 382-403¹ 345 135 107 μg/m³ *Not an example ofthis invention. ¹Range of values from duplicate experiments. ²PEI ispolyethyleneimine.

When the antioxidant is present by itself (Comp. A), acetaldehyde andpropionaldehyde values in particular are quite high, as are totalaldehydes. Adding a 600 molecular weight polyethyleneimine (Comp. SampleB) by itself achieves a moderate reduction in aldehyde emissions.

Adding the 600 molecular weight polyethyleneimine together with sodiumbisulfite (Comp. Sample C) is very effective in reducing all aldehydes.Surprisingly, however, replacing the 600 molecular weightpolyethyleneimine with a 275 molecular weight polyethyleneamine (Ex. 1)results in a further 20% reduction from the already very low emissionsexhibited by Comp. Sample C.

What is claimed is:
 1. A process for producing a polyurethane foamcomprising forming a reaction mixture that contains an aromaticpolyisocyanate, at least one isocyanate-reactive material having anaverage functionality of at least 2 and an equivalent weight of at least200 per isocyanate-reactive group, at least one blowing agent, at leastone surfactant and at least one catalyst, and curing the reactionmixture in the presence of (i) from 0.03 to 0.25 parts by weight of apolyethyleneamine mixture having a number average molecular weight of atleast 225 and up to 325 per 100 parts by weight of the at least oneisocyanate reactive compound having at least two isocyanate-reactivegroups per molecule and an equivalent weight of at least 200 perisocyanate-reactive group, (ii) 0.025 to 0.25 parts by weight of sodiumhydrogen sulfite per 100 parts by weight of the at least one isocyanatereactive compound having at least two isocyanate-reactive groups permolecule and an equivalent weight of at least 200 perisocyanate-reactive group and (iii) an antioxidant which is a phenoliccompound, to form the polyurethane foam.
 2. A method for reducingaldehyde emissions from a polyurethane foam, comprising: a) combining(i) a polyethyleneamine mixture having a number average molecular weightof at least 225 and up to 325, (ii) sodium hydrogen sulfite and (iii)and antioxidant which is a phenolic compound with at least oneisocyanate-reactive material having an average functionality of at least2 and an equivalent weight of at least 200 per isocyanate-reactive groupin amounts to provide 0.03 to 0.25 parts by weight of thepolyethyleneamine mixture and 0.025 to 0.25 parts by weight of thesodium hydrogen sulfite per 100 parts by weight of the at least oneisocyanate reactive compound having at least two isocyanate-reactivegroups per molecule and an equivalent weight of at least 200 perisocyanate-reactive group to form a mixture and then b) combining themixture from step a) with at least one organic polyisocyanate and curingthe resulting reaction mixture in the presence of at least one blowingagent, at least one surfactant and at least one catalyst to form apolyurethane foam.
 3. The process of claim 1 wherein thepolyethyleneamine mixture includes compounds having either of thefollowing structures I and II:

wherein x and y each are positive numbers, z is zero or a positivenumber and each R is independently hydrogen, ethyleneamine or linear,branched and/or cyclic polyethyleneamine.
 4. The method of claim 1wherein the antioxidant is present in an amount of 0.2 to 1.5 parts byweight per 100 parts by weight of the at least one isocyanate reactivecompound having at least two isocyanate-reactive groups per molecule andan equivalent weight of at least 200 per isocyanate-reactive group.
 5. Apolyurethane foam made in accordance with the process of claim 1.